[HN Gopher] So you want to learn physics (2021)
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So you want to learn physics (2021)
Author : weird_science
Score : 277 points
Date : 2023-08-20 16:28 UTC (6 hours ago)
(HTM) web link (www.susanrigetti.com)
(TXT) w3m dump (www.susanrigetti.com)
| EvgeniyZh wrote:
| Surprised to not find Tong's notes for qft [1] (his other notes
| are great too). That's the only clear source of introductory QFT
| (and I have none for advanced QFT). Of course the only real way
| to learn QFT is to learn it multiple times from various sources,
| but you usually have exam after the first one, and Tong may get
| you through it.
|
| [1] https://www.damtp.cam.ac.uk/user/tong/qft.html
| qsort wrote:
| A point that's rightfully emphasized by the author:
|
| > Solving problems is the only way to understand physics. There's
| no way around it.
|
| This generalizes well to other fields. I don't want to discourage
| anybody from trying to educate themselves in a difficult field
| (be it physics or something else), but that's a very common and
| immediately visible problem with autodidacts. If you haven't
| worked through enough hard problems you lack the intuition that
| ties together theory.
| belugacat wrote:
| That's a POV I've grown to adopt as I got older (like many,
| perhaps). I used to heavily privilege theory, believing that
| everything could (and maybe should) be derived from first
| principles.
|
| Now I place the concrete over everything else; theory is nice
| when it can illuminate why the practice works. Otherwise, it's
| just words.
|
| The most frustrating is when I have friends who have derived
| their entire understanding of a subject I know as a
| practitioner (typically something tech/programming related)
| from watching YouTube videos/listening to podcasts.
|
| Because they've heard hours and hours from experts, they have a
| feeling of deep understanding. But talking to them about this
| topic is extremely frustrating because their knowledge clearly
| has never had to be applied to the real world, and is grounded
| in nothingness, so they misunderstand lots, but they feel like
| they know what they're talking about as much as you do.
| civilitty wrote:
| _> That's a POV I've grown to adopt as I got older (like
| many, perhaps). I used to heavily privilege theory, believing
| that everything could (and maybe should) be derived from
| first principles.
|
| > Now I place the concrete over everything else; theory is
| nice when it can illuminate why the practice works.
| Otherwise, it's just words._
|
| That mirrors the trajectory of all humankind, doesn't it?
| From lofty Platonic ideals to nitty gritty empiricism and
| experimentation.
| tourgen wrote:
| [dead]
| antegamisou wrote:
| > The most frustrating is when I have friends who have
| derived their entire understanding of a subject I know as a
| practitioner (typically something tech/programming related)
| from watching YouTube videos/listening to podcasts.
|
| > Because they've heard hours and hours from experts, they
| have a feeling of deep understanding. But talking to them
| about this topic is extremely frustrating because their
| knowledge clearly has never had to be applied to the real
| world, and is grounded in nothingness, so they misunderstand
| lots, but they feel like they know what they're talking about
| as much as you do.
|
| You just gave the most accurate description of HN userbase in
| two paragraphs.
| beltsazar wrote:
| >> Solving problems is the only way to understand physics.
| There's no way around it.
|
| The reason is that you think you understand what you read, but
| as Richard Feynman said:
|
| > The first principle is that you must not fool yourself, and
| you are the easiest person to fool.
|
| You think you understand 90% of what you read, but in reality
| it's probably only 20-30%. By doing the exercises, at the very
| least you'll know that you don't know that much. And if you
| then reread the materials a few pages before, you'll realize
| that you have skimmed (or worse, skipped) some parts because
| you mistakenly thought you already understood it.
|
| Another tips from my personal experience: When you're reading a
| textbook, keep asking in your mind questions with the types of
| "what if" and "how about," which are sometimes not yet
| explained in the section you're reading. Also, keep associating
| what you've recently learned with what you've already known
| (days ago, years ago).
|
| Be curious and validate that you really understand what you
| think you understand.
| markus_zhang wrote:
| It used to pose as a difficulty for self leaners because they
| did not have access to assignments, exams and solutions unless
| they register for classes.
|
| Nowadays it's a lot easier when there are so many free
| materials from top school online. And stack exchange and reddit
| is available almost 24-7 if one ever has a question.
| Qem wrote:
| > It used to pose as a difficulty for self leaners because
| they did not have access to assignments, exams and solutions
| unless they register for classes.
|
| Many textbooks still employ the deplorable practice of not
| presenting the answer to all exercises at the end,
| unfortunately.
| javajosh wrote:
| Yes, and I'd take it further. What I'd like to see more of in
| physics texts is presenting a problem _before_ offering the
| solution. Too often you get what amounts to a laundry list of
| techniques and ideas, which are the components to the answers
| to hard problems, but the student isn 't motivated to learn
| them. If you present the hard problem first, the student may
| flail around and realize: I need something to help with this!
| Now that they know they need it, and why, you can give them the
| tool that fits the bill. For example, I think calculus is
| probably better learned _after_ trying to write down some force
| laws, and perhaps doing some numerical analysis. Then when you
| learn them you realize those nice closed-form solutions aren 't
| busywork, they are _huge_ labor saving tools that eliminate ad
| hoc labor intensive analysis.
|
| I would also _deemphasize_ the more mathy parts of calculus -
| do you really need a deep dive into continuity or the
| fundamental theorem of calculus? Eventually, yes. But it 's
| just like programming: you're not going to need to understand
| language theory or ADTs or category theory or lambda calculus
| to write your first program. Or your second. And, IMHO, you
| should only reach for this understanding when you realize you
| need it. Otherwise, it won't integrate well into your toolkit.
| whartung wrote:
| > If you present the hard problem first, the student may
| flail around and realize: I need something to help with this!
|
| I suffer from this. Sure, I'd like to learn physics, but what
| I don't want to do is learn all of it. Right now. Because
| what I'd rather learn is what I need to solve the problem I
| have. It's a silly problem, it's not real world, but it's my
| problem that I'd like solved.
|
| As I've grabbed my horse and lance and rushed at this
| windmill from assorted directions, I quickly run into my
| limitations that prevent the problem being solved. I run into
| vocabulary problems with the math, the fact that I simply
| don't have the math to approach the problem (which appears to
| be some vector calculus -- I think. "No, you idiot, it's XYZ
| instead", but I don't know enough to know that it's not
| vector calculus, if, indeed, it isn't). I try to apply basic
| kinematics to the problem, but I don't know if that's enough.
| And, finally, it could be all of those things plus, oh, some
| optimization issues and, also, would you like to be
| introduced to the several different techniques for computing
| numeric integration and the differential equation solvers?
|
| "Eeep!"
|
| To quote the film "Addams Family Values":
| Wednesday: Pugsley, the baby weighs 10 pounds, the cannonball
| weighs 20 pounds. Which will hit the stone walkway first?
| Pugsley: I'm still on fractions.
|
| So, yea, that's me, I'm Pugsley. It seems I need 2+ years of
| mechanics, calculus, and differential equations, and,
| probably, some time with computer based simulation all to
| chart the course for a spaceship to a planet for a 40 year
| old role playing game. Of course, I don't know what the,
| perhaps, abbreviated path I could take through those domains
| to get to be able to answer my question. That might knock a
| year off the study, but, unlikely. "Better to have all of the
| foundation" and all that. Which is true, but I'm kind of
| after the "reward" part here, not so much the "journey".
| projectileboy wrote:
| You might dig "The Theoretical Minimum" by Susskind, as
| well as his follow-on books. And he has associated lectures
| on YouTube.
| brightlancer wrote:
| > What I'd like to see more of in physics texts is presenting
| a problem before offering the solution.
|
| Yes.
|
| > If you present the hard problem first, the student may
| flail around and realize: I need something to help with this!
| Now that they know they need it, and why, you can give them
| the tool that fits the bill.
|
| No.
|
| If an instructor deliberately gives a student a problem that
| they know the student _cannot_ solve, then it rightfully
| destroys trust.
|
| I never taught at the university level, but with middle and
| high school math students I taught them to how (re)discover
| the solutions, rather than teaching them the solutions
| directly.
|
| As a practical matter, many of my college classes went too
| quickly to do anything _but_ teach the solution -- or tell us
| to learn it between classes and bring questions back.
| javajosh wrote:
| I don't think it breaks trust, if you tell them what's
| going on. "Hey kids, I'm going to give you a problem that
| went unsolved until Newton. I don't expect you to find his
| answer, which I'll teach you later, but I want you to try
| to solve it your own way."
| aleph_minus_one wrote:
| > If an instructor deliberately gives a student a problem
| that they know the student _cannot_ solve, then it
| rightfully destroys trust.
|
| This does not destroy trust, but gives the student an
| important lesson: we only have the techniques to solve,
| say, 0.0000001% of the problems. So you have to learn
| brutally hard for the next many years (or rather decades)
| to have the minimal qualifications to be able to invent
| whole new techniques that no person has ever come up in
| history before to increase this ratio from, say,to
| 0.000000100000000001% (even this would trigger a whole new
| aera in the history of science).
| BenFranklin100 wrote:
| I only became reasonably proficient in physics when I took the
| summer off between undergrad and graduate school and spent
| three months, six days a week, ten hours a day, doing nothing
| but working through four years of undergraduate physics
| curriculum by solving problems from my textbooks.
|
| There is no substitute for solving problems.
| ak_111 wrote:
| That is some dedication, well done. Interesting to know more
| about your career and where this lead to if you continued
| down the physics path.
| BenFranklin100 wrote:
| I went on to earn a doctorate in biophysics and then began
| a career developing instrumentation for biomedical
| research. While I no longer work directly in the field of
| physics, the physical intuition and reasoning abilities
| honed by a physics education has allowed me to successfully
| lead teams consisting of electrical and mechanical
| engineers, while serving as the liaison to biologists and
| doctors. I regard a physics education as a modern-day
| 'liberal arts' technical degree.
| shanusmagnus wrote:
| Like another commenter, I'm curious what drove you to this.
| Seems like clearly A Good Idea I Could Have Benefited From,
| but my attitude was always: I finished the class, whatever I
| need to learn through application, life will point me toward.
| Yet I wish I had done something similar to what you did. What
| gave you the impetus?
| BenFranklin100 wrote:
| We were required (by the state I believe) to take a
| comprehensive test assessing our competency at physics. I
| struggled with test and was disheartened that four years of
| strenuous effort would be all for naught. I knew I needed
| to do something to shore up my understanding of physics if
| I was going to retain the knowledge decades onwards. The
| other reason was a simple love for the beauty and
| underlying simplicity of the subject.
| [deleted]
| remote_phone wrote:
| In college, I was always the first one out of my friends to
| "get" a concept, like fast Fourier transforms, anything with
| signal processing or even coding or any labs we had to do etc
| so I would spend time teaching them in the library. However I
| never did any of the exercises, mostly due to laziness and not
| arrogance. They would get A's and I would get C's and D's.
|
| I emphasize this story to my kids because knowing isn't
| important because everyone eventually figure it out. It's the
| ones who can do the problems and get good marks that succeed in
| the end.
| froggit wrote:
| This is kind of interesting to hear because I was the other
| way around. I found the best way to understand something was
| to teach it to others. That way I took what I already
| understood and was able to see what other people
| misunderstood, which was often something I'd never expected
| to be an issue, and add their experience in learning the
| topic on to what I already knew which expanded my overall
| understanding.
|
| Then again, in the process of teaching I always found myself
| teaching people to work problems, which required me to be
| able to work the problems myself. In a way, it's kind of
| impressive you managed to avoid doing that.
| javajosh wrote:
| I think this shows a lack of self-doubt, which can be deadly.
| Those problems acted as verification _to yourself_ that you
| understood the theory and its application. If you truly
| understood the material, then the problems would be zero
| effort. However, if you struggled with them it 's a signal
| that you don't know what you think you know.
| TheCleric wrote:
| As someone who had an a similar experience to whom you are
| replying to, this was definitely not the case. The problems
| were easy, but were not "zero effort". Even if it takes you
| only a few minutes to do the steps and show the work per
| problem, then that could still take you 30-60 minutes to
| complete the assignment. That was time I'd spend doing
| things I wanted to do (fun in the short term, a nightmare
| in the long term).
| ChuckMcM wrote:
| Totally 100% with this. When younger I thought I could read the
| material and say "Oh, okay that makes sense I understand this."
| Only to fail miserably when on a test or somewhere I had to
| apply what I "knew" and realizing I didn't actually know it. I
| lean strongly toward autodidacticism and learned that if I
| could solve problems with the technique _then_ I knew it.
| ecshafer wrote:
| My calculus 1 professor gave the advice that the best way to
| study is to do every problem in the book, then go and get
| another book and do every problem in that book, and keep
| doing that until you look at a problem and know exactly every
| step to do immediately.
| ChuckMcM wrote:
| Time consuming but I can see this being really really
| effective.
| SpaceManNabs wrote:
| I see no mention of Landau and Lifshitz! On a less joking tone, I
| don't know many of these books. I was kinda surprised. guess i am
| outdated.
| gaze wrote:
| Landafschitz is kinda hard to self teach from. Fantastic
| supplement, though
| cgh wrote:
| To help with some of the math required by general relativity,
| there's a good series on YouTube by the user "eigenchris" on
| tensor calculus, which I found helpful for a geometric intuition
| of what's going on. He also has a series on GR itself, which I
| haven't watched yet. If you're interested in learning GR and want
| specific information on the area of differential geometry you'll
| need to understand it, then this series is a great start.
| rollinDyno wrote:
| This post comes in at a very good time because I have recently
| begun to become interested in particle physics and have so far
| only resorted to watching YouTube videos. This is a sign that it
| is maybe time for me to jump into a textbook.
|
| However, I seem to be interested in a few particular questions
| about particle physics as a science rather than facts about
| particle physics. For instance, I am interested in the
| instruments and methods that physicists use to verify their
| theoretical claims empirically. I am also interested in how
| theorists are able to come up with theories so early on, such
| that they are confirmed by evidence many years later. What are
| the assumptions that they were able to make? I am curious about
| where they derived the creativity to be able to bring in so many
| assumptions together and the come up with their models. Now that
| I write this, I realize that before theories were validated there
| were probably competing models.
|
| Therefore, I am not exactly sure I want to study particle physics
| per se, or whether a book on the history of particle physics will
| do. I am ok with having a popular understanding of the subject, I
| mostly want to gain inspiration from following the work of famous
| scientists.
| deepsquirrelnet wrote:
| Even though Susan Rigetti says you don't _need_ to learn calculus
| first, I would recommend it --- or learn it concurrently with the
| introductory mechanics course. Mechanics is so much more
| enriching when you learn the mathematical language that was
| created to describe it.
|
| You'll already be one step ahead by the time you get to the
| second course, which is good, because you can strongly benefit
| from learning vector calculus at that time. I really enjoyed the
| text "Div, Grad, Curl and all that".
| ghaff wrote:
| One problem with approaching physics without any calculus is
| that you're more or less in the place in which most people
| taking high school physics are. Here are a bunch of formulas.
| Memorize them and don't worry about why they are what they are
| or how they relate to all the other formulas that you also have
| to memorize.
| DigitalNoumena wrote:
| [dead]
| [deleted]
| cb321 wrote:
| Rather than 27 (or however many) books, an ambitious student
| _may_ be able to use _just one_ big-ish book: Ian D. Lawrie 's "A
| Unified Grand Tour Of Theoretical Physics". This even has a
| little 18 page "Snapshots of the Tour" which might be a trip down
| memory lane for those who studied physics long ago.
|
| Of course, it might also be impenetrable if you haven't had prior
| exposure to most of the material.. I have zero experience trying
| to teach physics from it.
| libraryofbabel wrote:
| It will be impossible to learn physics from this book, even in
| the unlikely event that you already have all the requisite
| mathematical background (partial differential equations, vector
| calculus, tensors, etc.). Degree of "ambition" doesn't come
| into it; you just can't start out with special and general
| relativity and spacetime and quantum fields; you need to solve
| a lot of problems in newtonian mechanics and electromagnetism
| and thermodynamics and get a solid foundation in classical
| physics first. There is no royal road to this stuff: Susan's
| list lays out the standard curriculum and it's really the only
| way we know to produce physicists.
|
| That said, this book does look like a great text for someone
| with a graduate level physics knowledge who wants to refresh
| their memory.
| fcatalan wrote:
| I dropped out of Physics back in the day, because I loved
| computers a bit more, and now that I'm kind of fed up with
| computers I'd like to remove the thorn and do something like
| this.
|
| But I find that so much time has passed that I would need to
| brush up parts of my high school maths first, and this kind of
| discourages me before even starting.
| monster_group wrote:
| I decided to start self learning theoretical physics late last
| year. I have been now studying physics every day for almost a
| year (before and after work). I did have to brush up on
| calculus and matrices but it came back very quickly (within a
| few days) after a 25 year gap so I'd say don't let that
| discourage you.
| computerfriend wrote:
| Excellent discipline. What topic are you focussing on?
| monster_group wrote:
| I have been working on quantum physics since March of this
| year and am hoping to complete the whole text book
| (Townsend) by end of the year. Then on to special
| relativity -> classical field theory in 2024, general
| relativity and QFT in 2025 and 2026 - at least that's the
| plan.
| markus_zhang wrote:
| I'm preparing to do something similar but attack a lesser beast
| that is the general relativity. I had a Master's degree in
| Statistics but unfortunately 1) Statistics does not really
| match Pure Mathematics and 2) I forgot most of it.
|
| A beast it still is, I think it is contained in its own walls.
| I can skip any topic in Quantum Physics and others that is
| irrelevant.
|
| I'm wondering if it's helpful to you too to focus on something
| smaller.
| ahelwer wrote:
| Using math to model a system instead of learning math qua math
| does wonders for ease of understanding. Derivates and integrals
| become easy if you're using them to model the relationship
| between position/velocity/acceleration. I don't think I really
| got linear algebra until using it to learn quantum computing.
| growingkittens wrote:
| Brushing up on high school maths is easy using Khan Academy, if
| that's all that's stopping you.
| nologic01 wrote:
| The title should probably be: "So you want to learn _theoretical_
| physics ".
|
| While generally little known and appreciated among modern
| theorists and mathematical physicists, physics is actually an
| _empirical_ science. In other words, every single section of that
| reading list is based directly or indirectly on a diverse and
| sophisticated set of devices and measurement configurations (aka
| experiments). Also, most progress in our understanding the
| physical universe follows simply from inventing ever better
| probes and opening new observation windows.
|
| A computer analogy of the theoretical/empirical physics relation
| might be fun: You can spend your whole life writing application
| software and never even know what digital devices you are
| actually using. That's totally legit. But if you want to write a
| new computer language (= a new theory) you most likely will have
| to dig into memory architectures and caches and all that stuff.
| If you want to dramatically increase the speed of computation (=
| a new observation window) you have to design a new chip. And if
| you want to go really deep and invent new computing paradigms,
| well then you need to learn quantum mechanics :-)
|
| In fairness, she does have a final sentence about that weird
| place called _laboratory_ (= a place of labor).
|
| > And, finally, a note on learning in a laboratory vs. learning
| from textbooks. Physics is both an experimental and theoretical
| science, and while research happens in laboratories and on
| blackboards and computers, the majority of any physics education
| does not take place in a laboratory but in lecture classes that
| teach from textbooks and assign homework problems that are found
| in textbooks.
|
| My recommendation for a comprehensive intro into theoretical
| physics is _The Road to Reality by Roger Penrose_. Alas there is
| no such profound review of all experimental physics.
| lanza wrote:
| She just lists the standard curriculum through undergraduate
| and graduate degrees. I clicked the links to all the books and
| my Amazon has the purchase dates from when I took those
| courses. It's not specific at all to theoretical physics.
| staunton wrote:
| [dead]
| xrayarx wrote:
| The author is aka Susan Fowler and author of three books and has
| a degree in physics.
|
| The Post is basically about how to get a degree or at least the
| equivalent and would require an effort of years.
|
| https://en.wikipedia.org/wiki/Susan_Rigetti
| kingkongjaffa wrote:
| It's a decent list but thermodynamics is introduced way too late
| in the list (after modern and quantum wtf) and fluid dynamics and
| fluid mechanics including aerodynamics is entirely missing.
|
| If you have a physics education (I have an engineering education)
| can you tell me if you can really get a physics degree without
| bumping into Bernoulli or Navier-Stokes?
|
| At least just to see the lay of the land.
| Avshalom wrote:
| I have a B.S. Physics from NMT graduated in 2009 (they changed
| some of the courses a year or two after my cohort) but the main
| series progression was Modern Physics -> Waves -> Classical
| Mechanics, E/M/Optics -> Quantum -> Thermo. Never really did
| much of anything fluids-wise other than some viscosity/drag
| stuff in Mechanics
| lanza wrote:
| Former theoretical physicist here (quantum gravity). TBH I
| don't know what Navier-Stokes is.
| ghaff wrote:
| Consider yourself lucky :-) Fluid dynamics and I never got
| along very well--probably mostly the math (partial
| differential equations mostly as I recall).
| disentanglement wrote:
| Thermodynamics is usually (and rightfully so) taught together
| with statistical physics for which quantum mechanics is
| essential, so the order does make sense.
| carabiner wrote:
| NS is too applied and seems akin to including the beam
| equation.
| kingkongjaffa wrote:
| Would you also say Maxwell's equations are "too applied"?
|
| They're both pretty firmly physics things rather than applied
| or engineering things, in their purest forms...
| btrettel wrote:
| I've noticed before that "physics" as in what is taught for a
| physics degree has gaps which make little sense to me as a
| mechanical engineer. Continuum mechanics (including both fluid
| and solid mechanics) is unfortunately nearly entirely absent
| aside from some basic things like Hooke's law and Bernoulli's
| principle.
|
| In my view, what's taught for a physics degree is more of a
| historical accident than a selection of the most important
| principles. In an extraterrestrial civilization, the boundaries
| between engineering, physics, and chemistry may be entirely
| different.
|
| Dismissing Navier-Stokes as just a consequence of Newton's laws
| and thus unimportant can be extended further towards dismissing
| a large fraction of what's taught in physics degree programs.
| An undergraduate physics student may get more education on
| Bose-Einstein condensates (which are just a consequence of
| quantum mechanics :-) than they do on Navier-Stokes. The
| Navier-Stokes equations are a lot more important than Bose-
| Einstein condensates in my view.
| lanza wrote:
| A physics undergraduate degree is different than a lot of
| degrees in that it's 100% incomplete for the purpose of
| training towards a real profession. Nobody hires physics
| bachelors. It's just the four year mark of your studies to be
| a 8+ year trained physicist.
|
| And for that purpose of being an intermediate degree to
| becoming a physics PhD, Navier-Stokes isn't relevant. You
| don't use it in most fields that are generating physics PhDs
| in the 2000s and beyond.
|
| There's only so much time to teach somebody in four years and
| there are _significantly more important things_ that are also
| being left out (e.g. more thorough courses on group theory).
| btrettel wrote:
| > You don't use [Navier-Stokes] in most fields that are
| generating physics PhDs in the 2000s and beyond.
|
| That's because physics _degrees_ don 't include much on
| fluid dynamics. If someone wants to get a PhD in fluid
| dynamics, they probably get a PhD in some variety of
| engineering. This goes back to what I said about the
| physics curriculum seeming weird to me, as it it's not
| about "physics" in itself. It's more a random selection of
| topics that exists for historical reasons.
|
| > There's only so much time to teach somebody in four years
| and there are _significantly more important things_ that
| are also being left out (e.g. more thorough courses on
| group theory).
|
| In another comment, you said that you don't know what the
| Navier-Stokes equations are. Given that, I don't think
| you're in a good position to judge their value.
|
| I have a couple of group theory books myself, and I don't
| agree with your assessment that group theory should get
| priority over fluid dynamics.
| lanza wrote:
| > In another comment, you said that you don't know what
| the Navier-Stokes equations are. Given that, I don't
| think you're in a good position to judge their value.
|
| It was an exaggeration given that it never came up during
| my studies once. And I think that's a fantastic
| assessment of their value that I made it through most of
| a decade of studies without having to know a thing about
| fluid dynamics.
|
| > I have a couple of group theory books myself, and I
| don't agree with your assessment that group theory should
| get priority over fluid dynamics.
|
| ...why? You're commenting on a physics line of education
| here. We don't use fluid dynamics and we _extensively_
| use group theory.
| staunton wrote:
| The physics curriculum prepares people to do research on
| stuff that is published in "physics journals". You may
| not think that should be the goal but it is. Doing work
| on Navier-Stokes lands you in a math journal on PDEs.
|
| On a more important note, the actual topics are
| completely irrelevant. What's important is learning to
| "think like a physicist". That's what has value even for
| those who don't go on to do academic research, which is
| most students. For any given physics topic that is
| relevant to real-life applications, there are engineers
| who _actually_ know how to use it, something that would
| be ridiculous to expect from the superficial treatment a
| physics degree _has to_ give any one topic.
| superposeur wrote:
| As a physicist, fluid mechanics was the most glaring gap in my
| undergraduate preparation, despite its centrality to most
| physics applications. Somehow it is always a "time permitting"
| topic at the end of an already-cramped curriculum.
|
| I first encountered the Euler equation in the context of GR --
| absurd. In another decade or two, I suspect its rightful place
| early in the physics curriculum will be emphasized.
| _dain_ wrote:
| >can you tell me if you can really get a physics degree without
| bumping into Bernoulli or Navier-Stokes?
|
| Bernoulli principle was covered in my bachelor degree but
| Navier Stokes wasn't; true-blue fluid dynamics was either an
| optional course that I didn't take or a grad student course, I
| don't remember now.
| elashri wrote:
| I am writing my physics PhD thesis and I did not study fluid
| mechanics (other than the few chapters in the standard general
| physics).
|
| It will really be dependent on what is your physics field but
| you can definitely survive in physics without deep knowledge of
| fluid mechanics except when your study require it
|
| PS: I am a particle physicist.
| jwuphysics wrote:
| A professor remarked that it was a bit sad that physics
| students nowadays have a better understanding of quantum
| field theory than fluid mechanics. He mentioned this while
| lecturing on QFT.
| [deleted]
| tekla wrote:
| But fluid mechanics is haarrddddd (Aeronautical Engineer).
| Compressible fluids can go suck it. I rue the day Navier-
| Stokes became a thing.
| elashri wrote:
| There is a more practical reason for that. QFT has become
| essential to learn for many Condensed matter physicists.
| And they always are with particle physicists which will
| span most of the physics community, at least comparing with
| whose work involve in-depth knowledge of fluid mechanics.
| Not to mention that QFT seems easy in comparison.
| pclmulqdq wrote:
| That is a very "pure physics" way to approach physics, and I
| think it's right if you want to build up the underlying
| principles. That was how my college taught physics, and it
| helped to make many otherwise unintuitive parts of
| thermodynamics understandable.
|
| Also, physicists don't necessarily include fluid dynamics as a
| core discipline. It is almost mechanical engineering to them.
| I'm not surprised to see it missing.
| carabiner wrote:
| yeah NS is just newton's laws, which is part of mechanics
| mhh__ wrote:
| Newton's laws and centuries worth of intuition about fluids
| but sure.
|
| Also stating the equation isn't the same thing as studying
| it.
| cli wrote:
| The order seems fine to me.
|
| Thermodynamics/statistical mechanics was taught as a junior
| level class at my undergraduate alma mater. During that year,
| students would take electrodynamics, classical mechanics, and
| statistical mechanics as separate classes in some loose order,
| although of course simpler versions of these topics would have
| been introduced in first year physics.
|
| The lack of fluid mechanics also, unfortunately, tracks with my
| experience.
| abhayhegde wrote:
| This guide does contain the books that are usually recommended in
| a university course setting! So, it will require significant
| amount of time and effort to master it. One of the series of
| books that physicists religiously stick to is Landau and
| Lifschitz. But my experience has been that it's worth it only if
| you already have some basic understanding.
| joe__f wrote:
| I never got on very well with Landau and Lifschitz it's pretty
| intense. I mostly used pdf lecture notes from different
| courses. They can be a bit mixed but many are very good quality
| and you can easily pick up a couple for the same topic if you
| don't understand some part of one of them
| ajkjk wrote:
| Landau and Lifschitz are terrible books, pedagogically
| speaking. They're good only in that they're exhaustive and
| rigorous.
| amluto wrote:
| This has the same omission that my undergrad program had:
| continuum mechanics. Even just the very basics (pressure,
| velocity, etc in a moving, non-equilibrium system) and
| translating between the terminology used by different science and
| engineering fields (static pressure, total pressure, velocity
| pressure, stagnation pressure, hydrostatic pressure, dynamic
| pressure, plain old pressure, head, oh my!) is very useful.
|
| Hydraulics are _everywhere_. Ever used a sink? Flushed a toilet?
| Contemplated an air filter? Felt both sides of a small fan?
| Wondered how, exactly, a utility pump causes water to go in the
| inlet and out the outlet, and tried to read the manufacturer's
| spec? Contemplated that the ripples when you throw a rock in an
| actual pond really don't resemble the average "look I made water
| in WebGL" animation very much?
|
| And more fancily, and very much in "Physics", cosmological models
| usually model the universe as being full of a spatially varying
| _continuous fluid_. Stars are plasma or weirder things, and those
| are fancy fluids.
|
| Yet, for some reason, the basics are missing from "Physics". You
| can sometimes find them in mechanical engineering departments,
| and Feynman covers it a bit in his lectures.
| meristem wrote:
| Do you have text/other sources suggestions for this? I agree
| with you, would like to learn more.
| antegamisou wrote:
| Halliday & Resnick _Fundamentals of Physics_ is what we used
| in AP as well as in freshman year at college. Covers most
| sections one needs to be familiar with to be physics literate
| (solid /fluid mechanics, waves, thermo, electromagnetism,
| optics, relativity).
| srameshc wrote:
| I love HN for thing like these that I wouldn't have otherwise
| found out. I used to think often about physics but not seriously
| enough to search for resources on how to get started and learn.
| But now that I have this guide (thank you Susan), I think I will
| start and no longer wonder or plan for learning physics in the
| future.
| projectileboy wrote:
| So happy to see the love for Griffith's Intro to Electrodynamics.
| I know it gets dinged for not being sufficiently rigorous, but
| I've never read another math or science textbook that did as good
| a job of getting a beginner to truly understand the subject.
| gleenn wrote:
| In what way is it not rigorous? I've never read it but it
| definitely seems interesting to have a "good" but non-rigorous
| science book. Does it just hand-wave over some things to get to
| other important topics?
| projectileboy wrote:
| I didn't think so, but it's the text I used as an undergrad,
| so I don't have a basis for comparison. I just have seen that
| criticism pop up on HN when this topic has arisen in the
| past.
| tayo42 wrote:
| > they are and have been dreadfully underserved and
| underestimated by the academic physics community (who do not take
| them seriously because they aren't studying at colleges and
| universities)
|
| This stuck out, pretty rigorous if all you want to satisfy your
| curiosity. If you want to actually apply any of the hard work you
| put in, you need a degree.
|
| I think that is the most interesting part of learning anything,
| applying it interesting ways. Doing that within so many of the
| areas of study is still gated behind academics.
|
| That killed my motivation for putting effort into most things,
| pretty much except computer science where we are still ok with
| trusting self taught people for some reason. But to do anything
| interesting physics, astronomy, philosophy too you need to be in
| school. sucks
| thrwaway99956 wrote:
| > That killed my motivation for putting effort into most
| things, pretty much except computer science where we are still
| ok with trusting self taught people for some reason.
|
| 100% same, except computers bore me to death now. I would even
| be willing to go back to school at this point if it wasn't tens
| of thousands of dollars.
| quantum_state wrote:
| " But to do anything interesting physics, astronomy, philosophy
| too you need to be in school." Why would you say that? I am
| curious. Imagine you are into a specific physics subject and
| knows what to do with some of contemporary problems that are
| puzzling people, work on it to provide your solution, etc., and
| publish your findings. I would think no one could prevent you.
| Right?
| sebg wrote:
| Previous posts, if you want to take a look at the comments there:
|
| https://news.ycombinator.com/from?site=susanrigetti.com
| dang wrote:
| Thanks! Macroexpanded:
|
| _So You Want to Learn Physics (2016)_ -
| https://news.ycombinator.com/item?id=24088985 - Aug 2020 (124
| comments)
|
| _So You Want to Learn Physics (2016)_ -
| https://news.ycombinator.com/item?id=18374994 - Nov 2018 (122
| comments)
|
| _So You Want to Learn Physics_ -
| https://news.ycombinator.com/item?id=12691963 - Oct 2016 (129
| comments)
| elashri wrote:
| > Classical Electrodynamics by Jackson (essential). This is the
| bible of classical electrodynamics, and everyone who works
| through either loves it or hates it (I loved it).
|
| I agree that there is a division between who loves that book
| (like the author) and the majority of the graduate students who
| had nightmares (and sometimes still gets). I like this goodreads
| review of the book [1]
|
| > A soul crushing technical manual written by a sadist that has
| served as the right of passage for physics PhDs since the dawn of
| time. Every single one of my professors studied this book, and
| every single one of them hates it with a passion. While I've no
| intention of becoming a professor, I still wonder, will my
| colleagues also inflict this torture on their students? Will the
| cycle be perpetuated ad infinitum? How many more aspiring
| physicists will we leave battered and bruised at the gates of
| insanity before switching to a textbook that seeks to make
| electrodynamics clear and intuitive rather than a mind-numbing
| trip through the seventh circle of hell?
|
| [1] https://www.goodreads.com/review/show/1266180525
|
| * personal note: If this book is really the bible of classical
| mechanics, then I'm atheist.
| libraryofbabel wrote:
| Well yes, but curious what book you would recommend instead for
| graduate electrodynamics? Note that she already recommends
| first studying Griffith's _Introduction to Electrodynamics_ at
| the undergraduate level (and that one is a true pleasure to
| read imho).
| elashri wrote:
| I'm happy that many professors start to use Zangwill's Modern
| Electrodynamics [1] textbook. It seems more focused on
| explaining things and don't assume that you know too much
| (which you usually have no idea if you should have known
| something or you just an idiot) like Jackson.
|
| [1] https://www.amazon.com/dp/0521896975/
| jore wrote:
| It is interesting that 2 years later the same reviewer changes
| their mind a bit:
|
| > Now, a few years after writing that review, I must return to
| say that as much as I hate this book, it's probably the best
| textbook that I have. I constantly return to it to reteach
| myself basic concepts or math. The problem with the text is
| that in order for it to be useful, you pretty much have to
| already understand the material. It's a dense, technical manual
| that, when paired with an easier to understand text such as
| Griffiths, grants tremendous power. Don't get me wrong, if
| there is a hell, I personally hope John David Jackson is
| burning in it right now, but I also have to tip my hat to him
| LYK-love wrote:
| After reading this blog, I'm ashamed. I just graduated from
| college. In my high school, the education of physics was so
| boring and tiresome that I even hated it at one point. For this
| reason, I chose computer science rather than physics as my major
| in college. Later, I gradually became interested in physics,
| however, due to the lack of good enough study habits, atmosphere
| and courage (which is a self-deprecating way of saying cowardice
| and laziness), until now I have not taken a step forward. This is
| the decision I regret most in my life. I am going to the United
| States to study for a master's degree in CS. Maybe I can learn
| some physics during the freetime of the two-year program because
| the educational resources in the United States are more
| abundant(perhaps).
| ChrisArchitect wrote:
| (2021)
|
| anything new here?
| cal85 wrote:
| All of it, to the users who haven't seen it posted here before.
| chucksmash wrote:
| It was mentioned in another comment thread[0] this morning.
| These things happen[1].
|
| [0]: https://news.ycombinator.com/item?id=37199307
|
| [1]: https://news.ycombinator.com/item?id=32795559
| ahelwer wrote:
| Undergraduate physics hasn't changed much in the past two
| years.
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